Target for x-ray tubes



Patented Apr. 19, 1927 UNITED STATES rarest caries.

HARVEY C. RENTSCI-ILER AND JOHN W. MARDEN, OF EAST GRANGE, NEW JERSEY,AS-

SIGNORS TO WESTINGHOUSE LAM COMPANY, A

VANIA.

No Drawing.

This invention relates to anti-cathodes or targets for Rontgen or X-raytubes, more especially to rare metals which are peculiarly adapted forsuch purpose.

It has been recognized for long time that the intensity of the X-raysgenerated in devices of this character is dependent upon the atomicweight of the anti-cathode or target. It is well known that the greaterthe atomic weight of the target, the greater the intensity of the X-raysemanating from the target. Kaye has arranged the metals having highatomic weights and which are suitable for X-ray targets on the basis offor platinum as follows, the values for uranium and thorium beingcalculatedz' Iantalum Of these metals, gold is unsuitable owing to itslow melting point. Platinum, iridium and osmium are practicallyeliminated on account of the scarcity of these metals. Uranium andthorium have not been used heretofore because it has been impossible toprepare them in a form suitable for anticathodes.

Many attempts have been made to produce the heavier rare metals, such asthorium and uranium, in pure, coherent, metallic form suitable fortargets and for other purposes, but such efforts have uniformly beenunsuccessful. So far as we are aware. no one hitherto has succeeded inproducing these metals in pure, coherent, metallic form, although thepowders of such metals are well known. metallic uranium in its pure,coherent form since it oxidizes very readily in the air and interactswith gases, such as oxygen,hydrogen, water vapor, and the like, withgreat ease.

We have recently discovered that various refractory metals, such asuranium and, thorium. may be readily obtained by sinteriug thesubstantially pure metal powders in a furnace-of special construction,under suit- It is especially difiicult to obtain CGBEORATION 0F PENNSYL-TARGET non X-RAY TUBES.

Application filed December 21, 1920. Serial No. 432,326.

able conditions. e have also found that, under suitable conditions,these metals may be produced in this furnace by heating the hydrides ina high vacuum and at a high temperature in such manner as to causecomplete dissociation and ultimate sintering to solid, coherent metalwith or without the metal passing through the molten condition. Thefurnace is described and claimed in Rentschler Patent 1,480,301, grantedJan. 8, 1924, on furnaces, and assigned to the VVestinghouse LampCompany. The method employed in the production of such coherent metalsand the products obtained thereby are described and claimed in ourcopending application, Serial No. 432,325., filed December 21, 1920, ona method of sintering metals, and assigned to the Westinghouse LampCompany.

In accordance with the method set forth, we generally prefer to mold orcompress a disk or pellet of metal powder, such as uranium or thorium,and place the same in a crucible or on a sheet of molybdenum or tungstenwhich is inserted within a closely wound coil in an evacuated chamber.Highfrequency current is passed through the coil which acts as aprimary, inducing secondary currents in the crucible or sheet and thepressed disk of metal powder, sintering the same and forming pure,coherent, metallic uranium or thorium.

Thorium has a melting: point in the neighborhood of 2020 to 2030 C.Uranium and thorium have the highest atomic weights known, namely 232and 238.5, respectively.

The intensity of emission of X-ravs from these metals is in theneighborhood of 20% to 25% greater than the intensity of emission ofrays from platinum. We believe that we are the first to have obtainedsatisfactory X-ray targets which have atomic weights above 200.

X-ray targets of thorium and uranium are eminently suitable for rayemission since their melting points are comparatively high and. theiratomic weights are among the highest known. They are far superior to themetal tungsten previously in common use. a

We do not wish to restrict ourselves to the use of the pure metals aloneas X-ray targets, but we may use alloys or mixtures of uranium withthorium or either of these metals with other metals. If desired, theX-ray tube may be fillecl with an inert gas, such as argon, helium, andthe like.

lVe claim as our invention:

1. In an X-ray tube, a target of coherent metal having an atomic weightbetween 5230 antl 24.0.

In an X-ray tube, a target of dense CO- hevent metallic thorium.

3. in an X-ray tube, a target of substantially pure coherent metallicthorium.

at. An anticathotle comprising a coherent metal having an atomic weightbetween 230 and 240.

5. An anticathocle comprising coherent, metallic thorium.

6. An anticathocle comprising substantially pure, coherent, metallicthorium.

7. A target for X-ray tubes and the like consisting partly of: a,substantially pure, coherent metal having an atomic Weight above 230.

S.'A target :tor X-ray tubes and the like consisting of a substantiallypure, coherent metal having an atomic Weight above 230.

9. A. target to! X-ray tubes and the like consisting partly ofsubstantially pure, coherent thorium.

1!). A target for X-ray tubes and the like consisting of substantiallypure, coherent thorium.

In testimony whereof, We have hereunto subscribed our names this th dayof De cember, 1920.

HARVEY C. R-ENTSCHLER. JOHN T. MARDEN.

